Belt type oil skimmers, such as that described in U.S. Pat. No. 5,378,371, issued Jan. 3, 1995, to the assignee of this patent and entitled Method of Removing Oil From Water and Apparatus Therefore, (the '371 Patent) are well known. While oil skimmers of the belt type have been successfully used for removing oil from the surface of water, they have been unsuited for removing highly viscous hydrocarbons, such as grease, from bodies of water.
Most, if not all, commercially successful belt type oil skimmers, have used a single driven head pulley, an endless belt, and in the usual case a tail pulley which is at least partially immersed in the body of water from which contaminating hydrocarbons are being removed. Surface oils adhere to a descending reach of the belt and are thence carried upwardly by an ascending reach of the belt to a wiper location. Typically the wiper location is near the top of the descending reach and near the head pulley.
When attempts have been made to use the typical prior belt type oil skimmer to remove highly viscous hydrocarbons, such as grease, from bodies of water, the result each time has been a failed attempt. Unlike low viscosity oil, the grease, will not flow over the wipers and drop into a collection vessel below the wiper, but rather tends to collect against the wiper and the belt and "ball up". To the extent the grease does fall into a collection trough below the wiper, it tends to stay there rather than flow out and in a short time the collection trough is filled such that the entire skimmer is rendered useless for its intended purpose.
While there have been proposals for variations of drive systems for oil skimmer belts, such as training the belt over a roll, thence along a horizontal span to a pair of pinch rolls before traversing into the descending reach, no provisions are made which render such skimmers useful for greases which only flow at higher temperatures and other high viscosity hydrocarbon removal.
One proposal would use a conveyor with projecting spikes to remove tar and, allegedly, oil from the surface of a body of water. The tar adheres to the spikes as the conveyor belt is passed into and out of a body of water having tar and possibly other hydrocarbons on its surface. As the spikes pass through the tar, and perhaps other hydrocarbons, the hydrocarbons adhere to the spikes. As the belt commences its downward travel from the top of the conveyor, the spikes pass between a row of tines which are heated and effective to at least partially remove the tar from the spikes. It is proposed that heating of the tar would produce molten tar which could flow to a collection tank.